A change in mapping can make a big difference to the way the bike feels and responds to the throttle. It can alter the way the power comes in and how the bike revs out. It can't generate lots more power like a 280 or 300 conversion can but will make a noticeable difference from a soft beginners map to a harsh expert/dry weather map.
Difficulty I find is having time and finding a suitable section to try them on back to back. Especially if trying similar maps. I have switchable PTB and have a played with a few maps. I had a 05 with Sains map which I liked and never changed, My current 09 came with "mild and wild" and a 280 kit and hated the maps (mild too flat and wild was very sharp but felt to drop off higher revs compared to Sains and on double blip step I missed the second stage of throttle response).
Changed to my Sains map and a Mitani 280 map which felt a little similar and bike felt much better and similar to what I was used to. However changed back to a 250 as 280 seemed to be dragging me around.
I stick with Sains map as main map and have tried several maps in the second map. Have tried 250 mitani which is very similar, tried a Scott map from Sandifords which felt a bit like Sains at lower end but flatter at higher revs and I think more efficient. Currently have OTAR5 off http://members.quicknet.nl/sw.zeinstra/4RT/index.htm
Which feels again similar to Sains but flatter and softer. However I find it a little lacking having got so used to Sains map that I tend not to use it. I think if you switch to a map then it is better to get used to it and not use 2 maps in a trial unless maybe you run a soft map as standard and then have a more powerful/aggressive map just for when you need it.
The web site mentioned above has several maps and software downloads which can compare maps.
Anybody else's comments to maps they like would be interesting. I am currently looking at a suitable map for friends bike as he is finding a sains map a little too much for his style of riding -looking for smooth map with minimal engine braking as he is a little harsh on and off the throttle.