I'm a mountain biker who would like to ride the road and non-singletrack over the winter and on days when the dirt trails are not rideable (I hate mud...).
So I'm torn between putting some different tires (and maybe a 2nd set of rims/other) on my current mountain bike and just buying a road bike.
My problem lies with the cost of a road bike (even if used) and what I'd get for the $. My mountain bike, which costs about $850 Canadian, has good components and is pretty light (for a mountain bike), but if I buy an affordable road bike (< $500) I'm concerned that the quality of the bike and components won't be good enough to really be better than my mountain bike which I can make "road worthy" for a few dollars.
Kind of depends on how long you're riding and how fast you want to ride. You probably want to get a road bike for distances longer than 30 miles. It is arguable on which is more comfortable over long distances (less aerodynamic and more resistance, but a better position vs. more aerodynamic and less resistance but not exactly as comfortable position-which is also arguable), but most people will go faster on a road bike. However, if you're just riding for an hour or two, I don't think you'll need a road bike. You probably won't go as far/fast as you could, but I don't think you'd need a $500 bike...slicks would do. Also, if the roads are in pretty poor shape, I'd recommend you stay with the mtb.
You may not want to get a cheap new road bike, just because components are as good. With some careful looking, you might be able to find a very good used road bike.
IMHO, an MTB with slicks is not really "road worthy". I have an MTB with two pairs of wheels. Knobbies on one pair for off-roading, and slicks on another pair for commuting. I commute on the MTB because I have some gravel sections that are a bit much for a road bike. But I would not want to take the MTB with slicks out for a road ride. I prefer a road bike...
1) Higher pressure tires. 2) More riding positions - especially the drops for fighting a strong headwind. The MTB doesn't really offer a good position for this. 3) Higher gearing - My MTB has a top gear of 46/12 and with the slicks, this is a 7.6m gear. A road bike should really have a top gear of at least 8.5m and if you have some steep hills, over 9m is even better.
