First of all, one thing that is very important:
Match is always better than no match. So, you should definitely use that match on your HSA if you've already maxed out the company match on your 401(k). In fact, for most people there won't be much reason to invest in your 401(k) above the company match at all.
If, for example, your company matches only up to 5%, and you want to invest 15% of income into retirement, you ought to open an IRA instead (Roth or standard depending on your situation) and put the extra 10% in there.
Beyond that, you're right, HSA's (the accounts themselves) have all the benefits of a 401(k). I wouldn't invest there for retirement instead an IRA, though. There is just no reason.
The only built-in downside of an HSA is the HDHP attachment, which may be undesirable to some employees or in certain situations.
If you want to get down to raw dollar figures and your company is offering both a standard health plan and a HDHP+HSA, the calculation will be dependent on the premiums and benefits of each and your projected costs of your health care (which is always a crystal ball estimation anyway). Those costs and benefits can vary wildly, from a completely obvious choice on either the HDHP or standard plan, or pretty much a wash where you decide based on your comfort level with a high deductible.
Standard plan: Your company might offer a standard plan that costs you $100 out of pocket for an individual. That means you pay a minimum of $1200 a year for health care. Most plans will have copays (a flat amount like $15 you pay for standard doctor consultations), a deductible (you pay 100% of fees up to this, co-pays don't count), a percentage you pay beyond the deductible (20% is typical), and a maximum (like $1000 per individual per year - beyond this, up to a "lifetime" maximum benefit of like $2 million, you won't be charged anything).
In a standard plan where you have no expenses, you might pay $1200 a year plus a couple co-pays, for a total of $1230. In a bad year with surgery, you might max out, so $1200 + $30 + $1000 = $2230.
HDHP/HSA: These plans are very different. You might still pay a premium, I.E. $30 a month. They will still have a deductible and maximum, but they might be the same amount. You will probably not have copays (I didn't when I had one, but I could be wrong), which means a standard doctor visit will cost more like $80-100.
In a good year, this will mean that you pocket $500 from your company, but pay back $360 in premiums. A couple doctor visits would mean there's only $300 left in your account at the end of the year. But, that's still a net cost of only $60, compared to $1230. Big win!
In a bad year, you would end up out of pocket the max (say $2000) plus premiums, minus the $500, for a total of $1860. In this case, still better than the standard plan.
The important difference will come in an in-between year. You will reach the max quicker on an HDHP than you will on a standard plan. With a family, where all of these numbers are higher, and you have more people to be getting sick/injured this might make the standard plan a better benefit.
However, since whatever you build up in an HSA account stays with you forever, while you're single and have only your own health to be concerned about, that is probably a good choice. When you have a family, things might change and you switch to a standard plan, but you still have that war-chest to offset copays and hospital visits in future years.
I was forced onto an HSA for 2 years with a smaller company. They had a really good contribution, $2500 if I remember right, and we saved up big time. Later, when my wife was pregnant, we were on a low-deductible standard plan and paid all our fees out of the HSA. It worked out great.
I say, as long as the averaged yearly expected costs make sense after doing calculations illustrated above, go for it!