I've been in the Army Guard for multiple years as well though I have no experience with post-residency life in the Guard. I will also add that notdeadyet and I joined under the ASR program which was a ridiculously good deal and is no longer available so while I'm sure we both try to be objective we are going to be positively biased. All the usual caveats of "Should you join the military?" still apply. That being said, barring prior service members close to retirement, I think the Guard or Reserve are by far the best way to go.
Control over your match, control over where you live, a civilian job with civilian pay, and (at least currently) shorter deployments are the major benefits.
The biggest challenge is that you now have two jobs and two bosses. Having to worry about scheduling around drill weekends and annual training can be a pain and it will definitely cost you personal time. I've seen medical students and residents held to standards anywhere from exactly what the non-physicians due to told not to worry about it and focus on school but you have to be ready for the worst (drilling every month and using 2 weeks of your vacation each year for annual training, add-on a deployment every 2 years once done with residency). Post-residency, you'll be limited to jobs that can tolerate your absence for a deployment meaning no small groups or solo practices. The Guard (and probably the Reserve) is far more heterogeneous than active duty army so it is hard to characterize what to expect.