I plan to make changes to the particle object so it supports stuff like particles which grow and rotate...of course the reason its so fast is it uses 1 vertex per particle...so if u use particles which grow and rotate then it will be like 1/4th the speed (you need 4 vertex for that)...but usually if you use particles that have texture and grow and stuff ur probably not likely to have 10,000 particles drawing on the screen at once...and if you did chances are it will slow down before the number of vertex become a problem.
As for collisions, adding a point collision option does sound like a good idea.... probably the best way to do it is to move along the x, test for collision...move along the y...test for collision...and from that determine if it should bounce left, right, up, down...and maybe some options like 'bounce' and 'bounce once' and 'stop'... anyway i'll see how I go...
Its kinda tricky to work out where the cut off point should be for particle features. Its better for you to use a sprite for shrapnel and stuff because u can manually control the tinting, size, movement, and handle collisions and stuff yourself. Whereas if you say wanted to have a black hole which sucked up particles then thats not possible at the moment with the particle object.
But at the same time...being able to easily add particle effects and tweak them at your leasure in the properties bar does produce better quality games ... and its quite likely you'll end up using the particle object to add particle effects in situations where you normally wouldn't have bothered coz it would take too much effort..... which results in better games that are more fun for me to play