Lenses for m4/3 cameras - Short opinions about the current m4/3 lenses is a piece by Thom Hogan at:- http://bythom.com/m43lenses.htm
Lots of people have weighed in with opinions as to how right he is and have come out with their own lists. Not wishing to left out on something as much fun as that! Here's mine.
Like Mr. Hogan I haven't used them all. The Panasonic 14mm f2.8 pancake, 100-300mm, 8mm fisheye and 3-D lens are missing from the list.
Panasonic 14-45mm f3.5-5.6
The lens that with the G1 started m4/3 as a system. This is an excellent lens for a kit zoom. Designed with Leica it really set the standard for the quality, lightweight lenses that followed. I used mine an awful lot. Because of the way that m4/3 cameras tend to be sold as kits, I think I've had 3 of these. I've usually sold the spare ones on ebay, which as they attracted good prices made the camera cheaper. It seems Panasonic aren't offering these as kit lenses anymore, so if you've got one it might be a good idea to hang onto it.
Panasonic 14-42mm f3.5-5.6
Panasonics replacement to the 14-45mm. Cheaper, lighter and smaller. This lens often gets a bad press and while its not particularly good wide open its pretty sharp at f5.6 - f11. It really comes into its own as a video lens. It has the same silent continuous focusing as the 14-140mm and produces excellent footage. Some people rate it below the 14-45mm, but from my experiences with it (limited as I haven't had it long) I think its very similar in terms of performance. Well worth keeping if you buy one as part of a kit.
Olympus 14-42mm f/3.5-5.6
Again because of camera/lens kits I've had a few of these. I've always liked this lens. It often got compared unfavourably to the Panasonic 14-45mm and I always thought that was unfair. Its an extending lens and has no stabilisation built in. I think its better than it gets credit for and very much on a par with the Panasonic standard zooms.
Panasonic 7-14mm f/4.0
Very wide, very expensive. Very light for what it is. Its a sharp lens and produces amazing images, particularly at 7mm. I did however have some issues with my copy. Firstly it produced a lot of CA and fringing and secondly that big exposed bulbous lens and fragile construction always worried me with concerns about possible damage. If you like ultra-wide then its a great lens, though there's a fair amount of distortion. Fixed f4 aperture is very useful.
Olympus 9-18mm f/4-5.6
I think this a great lens. I've spent a long time looking for a good wide-angle that produces results like a standard prime and this is the closest I've found. It produces very sharp results, even wide open and at f8-f11 its very very good indeed. I like the size, its tiny, and I don't feel so concerned about damaging it. Its very good for CA and fringing as well. Whether you choose this over the Panasonic 7-14mm depends on how important those 2mm are. They do make a significant difference with lenses at these focal lengths and there's no denying that the 7mm on a GH1 or 2 at the 16:9 ratio using the full width of the sensor is impressively wide. I do however prefer the Olympus, for my uses.
Olympus 17mm f/2.8
10/10 for style, 5/10 for content. Somewhat of a disappointment. It does look great but mine performed pretty poorly with lots of CA and fringing. Mine was reasonably sharp but needed stopping down to f8 or so to get that. It doesn't compare well with the lens immediately below.
Panasonic 20mm f/1.7
I loved this lens the first day I tried it and I still do. I said then it produced the best results wide-open I'd ever seen and it was one of the best lenses I'd ever used on any system. I still stand by that. This is the lens that really demonstrates what m4/3 can do. It's wonderfully sharp, at all apertures, and its performance at f1.7 sets the benchmark for other lenses. I'm far from alone in praising it's virtues and if you were wondering if it lives up to the hype - It does!