Good person to ask would be one of the Citi/Comutacar owners (yes, I know Ben owns one of those too, but hasn't really be driving it yet). They're fixed gear vehicles.
250A will give you less than "normal" acceleration.
When we had the 225A controler in the ForkenSwift, I measured 36 seconds to get to 30 mph - on a fresh charge, on level ground. And that's using 3 or 4 gears to keep the pot boiling just right. That'll get you honked at etc., in most places if traffic can't go around you. (The 400A controller is good for around 25 seconds to 30 mph.)
But Mike D claims acceptable acceleration from his fixed-gear e-5th wheel using a 275A Curtis & Etek PM brushed DC motor:
Finding The Best Hybrid Mix - MIMA Honda Insight Modified Integrated Motor Assist Tour De Sol
If you go with a brushed DC motor... sprag clutch!