The potential problems with removal of runner are dependent upon how the runner was installed. Some dearies actually tack the runner to the steps, tread and riser. Ouch, because removal leaves those holes to be filled and stained to match (very difficult to conceal). An alternative method is to use carpet bars which come in wood or metal, in an assortment of finishes. This is slightly more expensive but imo, also *looks* more luxurious. The carpet is barred at the back of the tread where it meets the riser; best practice has the runner tacked beneath each tread rather than slanted from top-front to the back of the next lower riser. Note that under-tread tacking also uses the most running feet of carpet, so the most finished appearance is going to cost. There are several other methods, so discuss intent with the installer before s/he does the work. One thing for sure, is to not use any sort of sticky-back tape: it either doesn't hold well, or holds too well and removel is labor-intensive. Because of the carpet pile height, if possible choose treads that are slightly deeper than usual so as to maintain fully safe depth.

Most economical = carpet. After that, a solid finish (wood, cork, vinyl, tile, stone, etc) will require all the extras. Painted stairs will work...with plenty of elbow grease and with the FULL UNDERSTANDING the paint will wear/chip/"patina" inside of a few years. There are ways to lay a runner on the stairs and then trim out the edges of the tread/riser with wood-looking stuff. This will cut the cost in half of what I mention above. The other option is to place the runner and PAINT out the edges....creating a faux-painted-wood look which could be very handsome yet extremely practical. Notice how carpet keeps on coming up again and again? Yah. There's a reason for that. Those are builder grades stairs made for carpet.

The key to the improvement was to have the carpet stay parallel with the wall on the pie shaped steps. This involves a lot of cutting and pattern matching, without a border and pattern it would have been far easier. The carpet is also a nice wool Karastan so it feels great on bare feet.

Add a 3/4" strip on the edge. Even with carpet wrapped treads, code still applies. If, the depth is not 11" minimum, you will need a overhang. 3/4" should bring you into code but, check your local codes.