I quite like the smoothed look. It is a DIY job or at least get a bodyshop involved.
Depends if you are handy at body work and got the time and space to do it!! Not to mention the patience!!
The proper way a good body shop would do it is to weld a plate over the recess / hole and then lead line the gaps before prepping and painting.
A bodger would nosh loads of filler in and prep and paint.
A good half way (and the one I do) is to weld the fillet over the gap as best as possible and then used filler to finsh rather than lead fill. You run a small risk of cracking over time, especially on bonnet, boots and doors (all the slamming) but its the easiest way. For de locking doors i'm a little lazy and don't weld metal in the holes left but use fibreglass from behind and then from the front. Never had a problem with this cracking yet.
Paint can be done yourself and the quality of the finish is 75% in the prep work. Flat colour can be blown in meaning whole panel respray not ness (but still prefferable), metalics and specials will need the whole panel redone. Before I was confident enough to do the final paint, I used to prep, prime, prep, prime etc until ready for the top coats, then take it to the body shop for top coating, saving a fair chunk of money.
Oh yeah I think they look cool! Does depend on the car and other mods. I'm into quite smooth, debadged lines on cars. Had a Old Skool Beetle that was completley smoothed, deseamed and blended into 4" wider arch's. Really suits some cars but not others.