I don't really understand why Streetlites are so hated by drivers. As a passenger I don't like when they rattle but drivers would have the time to go round and sellotape/bluetack/stick foam pads to the areas causing the rattles, would they not? And in terms of engine, whenever I've been on one which hasn't been derated/on limp mode, it's performance has been absolutely fine, comparable to a standard E200 and to be honest almost comparable to an E300. Given the same maintenance routine I wouldn't think a Streetlite would be any more likely to be in limp mode than an E300, would it?
My understanding from folks who have driven them...
The set up on delivery was quite bad. The gearboxes usually poorly mapped so lots of very short shifting so you had lots of clattering up and down. Also, braking was an issue with some retarders kicking on at the first tap of the brakes. Brakes are still a bit of an issue but they are better. My local operator is a First opco and I have a clear memory of a shocking run on the back road between Bristol and Bath. That said, a year later, it was clear on a run from Bristol to Clevedon that mods had been done. Also, performance is dependent on the engine spec and manufacturer.
Issues with limp mode can be a consequence of maintenance, but same with any vehicle.
FWIW, as a passenger, I think Streetlites (shorter ones) are generally a bit better than the comparative e200. Clearly, a Streetlite is not going to be as good as most heavyweights (e.g. B7RLE) in terms of ride quality - that said, one of the worst journeys I ever experienced was a First Omnicity which was horrendous.
We're now looking at the oldest Streetlites (the early WF versions) being 14 years old so they've been more durable than many suggested.