Buffer regions / owin to spatial object

Hello everybody.

I have a set of points and I want to calculate a buffer region within a
given distance from these points without using packages requiring other 
software (such as spgrass6). I have used function disc() for each
point and then union.owin() (both from spatstat) to merge the single
buffers.
The result is an object of class owin, but I would need to obtain an 
object representing the polygons enclosing this buffer.

1) Are there smarter ways to obtain the buffer region (the union.owin is
very slow when it comes to hundreds of points, as it must be applied to 
only two owin at a time)? It seems there isn't for buffers around 
polygons (as Adrian Baddeley wrote in a recent thread).

2) If not, how do I convert the owin object into a Spatial object? There 
are many functions doing the inverse, but I couldn't find any doing this
conversion.

Sorry if the questions are naive... I'm an R beginner :)

Thanks,
Giorgio Guzzetta