By trips, do you mean hiking trips (trekking)? Or do you mean "backpacking" in the "traveling across Europe and staying in hostels" sense?
I ask that because the pack you link to appears to be intended for the second group.
For hiking/trekking, a 45 liter pack may be large enough, but it depends entirely on one's other gear. Most beginning hikers take traditional gear and too much of it, in which case a 45L pack usually isn't big enough. On the other hand, an experienced lightweight or ultralight hiker can easily fit all their gear and a week of food inside a 45L pack.
Another issue is that the EC pack you mentioned weighs 4 pounds 9 ounces, which is a lot for a 45L pack. For lightweight hiking, it's easy enough to get a good pack in that size range for 2-3 pounds total weight. (The real ultralight hikers are using frameless rucksacks that weigh 8 or 9 *ounces*, and their total pack weight is about what that EC Pack weighs *empty*.) The REI Flash 45 is about the same price as the EC pack, and weighs half as much.
If you want to go hiking/trekking, then I would urge you to go to a backpacking/hiking specialty store and see different kinds of packs. Get fitted, and try them on with various weights of gear. It's usually best to buy your pack last -- once you know what other gear you have -- so it all fits.
Dunno about that particular pack, but completely agree with the comments by kbennet.
Of course it's challenging to "buy the pack last" insofar as you likely need some sort of backpack to get the experience with other gear first. If you can't borrow or even possibly rent one to do that, then make a best guess at where you'll ultimately want to be on the spectrum of "traditonal" to "light" to "ultralight" backpacking, in order to better estimate the volume needed, with the large caveat that a lot of things can be strapped or stuffed into mesh pockets external to the pack.
One other caveat with the number of days on a trip is whether you plan your trips to be unresupplied or not, i.e., for a 10-day trip do you carry all 10 days of food at the outset?
Also certainly weather and temperature issues, related to season, altitude, and overall location of your trip --- weather/temperature impacts various gear choices and thus total weight and volume of gear (as well as perhaps water and food carried).
"What brands are best" --- again, depends on where you're shooting for in terms of base weight. If you're looking at the "light" to "ultralight" part of the spectrum, I'd suggest looking at ULA, Gossamer Gear, SixMoonDesigns, Granite Gear. But REI's most recent lightest offerings aren't bad these days.
It also depends on what you personally prioritize when you say "best" --- weight, cost, durability, specific features, personal fit, color, volume, "style" ...
YMMV a lot depending on what you prioritize vs. what someone else might, so I suggest that you be a little leery about any generic recommendations of "best" on any gear item.
Like the others said, the weight and bulk of your other gear will decide the issue.
If you're looking at 25 - 30 pound loads, with some light gear (solo tent or tarp, canister stove and one pot, etc.) you might want to look at the Osprey Exos series packs - 46 might work, 58 almost certainly would. Both packs are on sale at Backcountry Gear right now (use the Portal in the tool bar above), for $146 and $175 - not a lot more than the pack you found, and top notch gear instead of (as someone else said) a pack that's mostly going to be carry-on luggage, with a little light hiking somewhere along the line.
Another issue is that the EC pack you mentioned weighs 4 pounds 9 ounces, which is a lot for a 45L pack.
I'm going to quote myself, and revise and extend my remarks (as they say in Congress.)
4 pounds 9 ounces may be a perfectly reasonable weight for that pack for airline travel (note that it has a top handle for easy lifting into the overhead compartment, according to the EC web page.) For that, durability is crucial -- more important than weight, anyway. So asking if this pack "is any good" is hard to answer without knowing, "For what?"
The people who hang out in this forum are devotees of light or ultralight backcountry hiking. In the eyes of the traditional hiking community, we are total whack jobs. Crazy. Going out with tiny packs and no safety gear and always calling for rescue and mooching food and gear from "real" hikers. (Just so you know where you are....) (None of that is true, but that is often how we are perceived.)
When I got out of the Army and first started civilian backpacking, I thought a 5 pound pack was absurd. A "real" backpack had to weigh at least 8 pounds to provide the support to carry the 65 pounds of gear and food that I needed for a simple summer weekend hike. Now I think a five pound pack is still absurd -- though I owned one as I made my way down the winding path to ultralight hiking, then back up a little to light hiking using a 2-pound pack and a 12-18 pound base load depending on the season.
Several points come out of this musing, I suppose:
1. That E.C. pack may be fine for many purposes, but I don't think any of them are light or ultralight backpacking.
2. As you gain hiking experience you will know more about what you need in a pack (and other gear.) Much better to rent the expensive stuff first, if possible. Many local and national outfitters do this.
3. As you gain more experience, you'll know more about what you *don't* need, and start on the path toward Lightness of Hiking. And you can stroll down that path as far as you like.
When I began lightweight hiking, I was able to pack 6 days worth of gear in a 3,100 ci pack. I had to lash the sleeping pad outside the pack and squish clothes & my sleeping bag into a compression sack, but it fit.
For people who are relatively new to lightweight backpacking, I'd recommend either ULA's or Six Moon Designs' packs; their larger models have frames, a good feature for people still cutting back weight. Gossamer Gear has some packs worth looking at too.
If you want to try the packs on first, your best bet might be REI, Granite Gear, or Golite brand packs. They're easier to find.
I am not as extreme as some of the folks here about weight--and I am a real cheapskate! But I bought a couple of Eureka 3900 packs at Walmart--seems like they were about $50 apiece. They carry enough for us to be out for a week. And we backpack in Yosemite, which means we have to use a bear vault.
But we do have very small sleeping bags, a great MSR pocket Rocket stove. Those are cheap and light. And we don't pack a lot of clothes. I would say that most people pack too many clothes. WE just expect to get dirty, and we bring stuff that can be washed easily and dried quickly.
For five days my pack will weigh about 30-35 pounds, and my wife's will be about 8-10 less than that.