Congrats on the new Forester. I got my '09 Forester back in early August, and absolutely love it. Before buying that Forester I owned another Forester for over 9 years. Great cars that aren't too big, yet can haul a lot of stuff and can take some serious abuse.
For filters I use Purolator PureOnes PL14612. They're solid filters and at 14-18 PSI have the highest release valve PSI that I've found for a non-OEM filter. I've thought about using the PureOne PL14610 b/c it's the same filter just about a half inch taller, and might switch to that once my warranty is done and I can start doing extended OCIs. There's plenty of space for the longer filter, so it's nice to know that's an option if needed.
On my last Forester I used non-OEM filters for about the last 6-7 years I had it and I never had any issue I could relate to the oil or filter. But if you're concerned about the reduce PSI on the release valve, then by all means use the OEM filters. It's not worth losing any sleep just to save a couple of dollars. So if using the OEM filter gives you peace of mind, then I suggest you do it.
If you haven't checked it out yet, I suggest looking under the Forester to see how easy it is to change the oil. Honestly, it's the easiest car that I know of. You don't need ramps or anything, everything is very easily accessible, and the filter is perfectly vertical so it can easily be pre-filled. The hardest part of doing an oil change comes from the fact that the oil filter is surrounded by the exhaust headers, it's not bad but you can't mindlessly remove the filter. That's why for my next change I'm thinking I might drain the oil hot, then grab a drink and let it cool down before doing the filter.
On my last Forester I used conventional the entire time I had it and I never had any oil problems. As someone mentioned already the non-turbo 2.5L Subaru engines are very easy on oil, so any SM oil will do.
With this Forester I currently have Havoline DS (dino) 5w-30 in there, and that's also what will be going in at the next oil change. The oil change after that (November'ish) I'm planning to switch it to synthetic to give synth a try. I've bought a few jugs of the M1 0w-30 b/c of the $10 rebate, and plan on seeing how that runs in it.
Currently my plan is to do a UOA on the second fill of Havoline DS, then do a UOA on the second fill of M1 0w-30, after that I'm thinking of doing two runs of Valvoline SynPower 5w-30 with another UOA on the second fill. That'll let me see how the engine is breaking in, and also decide on what oil I want to run.
If I do everything as I currently plan, I'll post my UOA as I get them done, however it'll take a while before I do them. I drive two cars, the Forester and an old beater SUV, b/c of that my mileage gets split between them. Like I said I got the Forester the beginning of last August, here we are in the middle of June and I have under 5k miles on it. So I'm doing about 6k miles per vehicle each year.
Lastly, Bill in Utah has a Forester (an '06 I think), and he's done a ton of UOAs, so if he posts on here check out what he says cause the engine hasn't changed too much in the past few years