The person that I've been borrowing the telephoto lens for my Pentax wants the lens back, so I'm stuck with two kit lenses. Since I rarely use my K-x now anyways, I might as well get the lens for my E-P1, but which lens should I get?

I could get the Four Thirds adapter (allowing me to use a lot more than one lens, considering how cheap they are) and then for now the Olympus 40-150mm, or I could just get the new 40-150mm for $200. I didn't exactly want to spend that much though, but I might have to.

Of course I can also just get another cheap zoom for the Pentax.

I would recommend the M.Zuiko 40-150mm even though it is at the top of your price range as it gives you AF which would be useful in quite a number of siturations. I would think it was worth the money.

I haven't been looking at the prices of legacy lenses recently but the old Olympus OM 100mm f/2 was somewhat overpriced when I last looked. The Nikon 105mm f/2.5 did have a good reputation but then you are up for an adapter too.

I only recently joined the micro 4/3 community withan EP-1 & a lumix G1 & found that using adapters I have utilised My Jupiter lenses, some Nikon fit lenses alng with My 14/42 & 40/150 Olympus lenses.
Dont be afraid of good adapter & certainly look at the 105 Nikor It is a belter.
Good luck

I could get the Four Thirds adapter (allowing me to use a lot more than one lens, considering how cheap they are) and then for now the Olympus 40-150mm, or I could just get the new 40-150mm for $200. I didn't exactly want to spend that much though, but I might have to.

I had the 4/3 40-150 and sold it - and then regretted selling it - and then saw one in a pawn shop just before Xmas for a price I couldn't leave....and then a used Panny adapter in a photo shop down the road for half the new price.

Now all I have to do is use the damn thing...

C-AF is not supported with the 4/3 adapter and the E-P1.  The benefit is that it doesn't spend all day seeking.  The manual says "not supported", but that doesn't mean it will not work, it just works extremely slow that you don't noticed if it works or not, lol.  Not sure if the E-Pl1/2 or E-P2 support the adapter with C-AF.  But, you have to figure that the "pro" model E-P3 would support C-AF and AF-tracking, otherwise everyone with legacy 4/3 lenses will get really pissed.  Plus, you can look forward to eventually buying up the Leica D panasonic lens.

C-AF is not supported with the 4/3 adapter and the E-P1. 

Which really annoyed me because it means its almost useless for video