- The 28mm F/1.8 pairs well with the 85mm as far as build quality, focusing speed, and color rendition goes - if you pretend it's an F/2.8 lens and not an F/1.8 lens (it's soft wide open for sure). For a while those were my only two lenses, the 28mm and the 85mm, and they were a great combo.
- The 35mm F/2 is decently sharp, but the copy I've played with I wouldn't say was any sharper than my 28mm was at comparable apertures. Plus, the bokeh was rough and it wasn't super contrasty. Oh, and the build quality and focusing motor are definitely dated.
- The 35mm F/1.4 is NOT "quite soft wide open" - it easily bests the other two lenses wide open (I'd say it bests them when they're stopped down a bit, too). It sharpens up a bit stopped down, but F/1.4 is perfectly useable - I have 13"x19" prints taken with that lens wide open that are pin sharp after post-processing.
If you can swing the cost, the 35L is the unquestionable winner. I've owned the 28mm twice trying to convince myself I'd be happy with it as a normal prime on my 60D, but after renting the 35L a few times I'm done fooling myself and am saving for the red ring.
If not, the 28mm is a great mate for the 85mm F/1.8 - they complement each other well.