I get asked this question a lot. It's surprisingly hard to answer, because it depends on what you consider important, and what you're willing to put up with.
Let's summarize the main pros and cons of San Diego Road Runner as compared to a conventional dialup retail ISP:
On the other hand, if you spend a lot of time on the Internet at home telecommuting or downloading large files off the web, the extra speed of Road Runner can be worth the cost and hassle. This is especially true if you have access to alternative mail and news servers (e.g., at work, at school, or through another ISP) so Road Runner's own abysmal mail and news servers aren't of concern to you.
Road Runner is also better than a dialup ISP if you need to access your machine(s) remotely (e.g., from work). Most ISPs charge a premium for outward demand dialing, or for 24-hour "nailed up" connections. Although Road Runner, like most dialup ISPs, assigns IP addresses dynamically, your machine can keep an address indefinitely as long as you leave it on. If you have access to a "friendly" network with direct Internet connectivity, you can set up a virtual subnet with a tunnel through Road Runner so you can support a whole LAN of machines with static IP addresses without having to pay Road Runner for extra IP addresses or for their so-called "commercial" service. (If you need true commercial-grade service -- particularly if you're going to host a high volume web server -- get a leased line to a regular ISP. Today's cable modems are not nearly reliable nor fast enough in the reverse direction to support a "commercial grade" service.)
You should also consider your traffic patterns. If you telecommute to a local San Diego company that's connected to CERFNet, the direct Road Runner/CERFnet link that was installed in early August is a big win. But not every company and university in San Diego is connected to CERFnet; if yours is connected elsewhere, then the path from Road Runner may still include MCI and the infamous MAE-West tie point in San Jose. This path may lose so many packets at peak times as to squander most or all of any speed advantage Road Runner may have over a dialup link to a local ISP with better connections.
I use Road Runner almost exclusively to tunnel IP packets between my home LAN and Qualcomm across the CERFnet link, or to the web proxy cache at SDSC. Since I read news and mail at Qualcomm and at home (where I run my own SMTP services), I rarely use Road Runner's web proxy, news or mail services. So the poor quality of these services as continually reported in the Road Runner local newsgroups is not a major concern to me. Road Runner claims they will be upgraded in another week; we'll see.
Don't let them do this! When they're done, insist that they ping your local cable router for at least 10 minutes. If you see any packet losses or large delays, refuse to accept the installation. Have them file a trouble ticket, and don't agree to pay for either the installation or the service until they resolve the problem. From personal experience, it can take weeks or months to resolve cable plant problems, and performance can be utterly abysmal during this time. Now that Road Runner no longer offers their money-back guarantee, it's even more important to make sure that your installation works before you pay them a single penny for it.