I currently own an Irwin 28 mKIV and love it as a low-budget family coastal cruiser. You can read my detailed review (production, history, specs, etc.) here
She's a great first boat (actually, my second boat) and will serve well as a weekender and small coastal cruiser. While the hull and deck hardware (oversized) is rugged enough, overall construction is probably on the light side and by my estimation on par for most mass-produced boats of the era competing for the same buyer. As with any coastal cruiser of this age, condition and owner maintenance is likely much more important than the manufacturer.
My boat is equipped with a tiller, and while I love the steering feel, it takes up a lot of room in the cockpit while sailing. At anchor or at the dock the tiller can be hinged back so it doesn't take up any room at all. If I had the choice, I'd prefer a wheel on this particular boat so that there is more room in the cockpit while under sail.
I spoke with Gene Gammons (former Irwin project manager and close friend of Ted Irwin) and was told the first I28 was built in 1970 with the last likely produced in the late 70's/early 80's. My boat is a 1978.
Here's a sample of the I28 review I wrote (referenced above):
"So what’s the take home message with all of these ratings, ratios and numbers? The Irwin 28 isn’t going to be the fastest sled for Wednesday night races (PHRF handicap rating of 213), but she’s likely a bit more comfortable (comfort rating of 26) and stable than other popular high volume production models from the same era. For example, the very popular Catalina 27 (std. rig) has a motion comfort rating of about 23.5 and a capsize ratio of 1.87. The O’day 28 has a motion comfort rating of 20.57 and a capsize ratio of 2.11. None of these boats are suitable as bluewater passagemakers, but they all make good coastal cruiser. Of the three, the Irwin may well be the most stable and comfortable while the O’day (PHRF handicap rating 204) would be a better choice if speed is a priority for your coastal cruise. The Catalina splits the difference (PHRF handicap rating 210).
In summary, the Irwin 28 is a fine coastal cruiser for those on a modest budget. She’s the perfect balance between the cramped accommodations of the 25-26 footers and the higher expenses of the ~30 footers of similar vintage. The slight spring in her sheerline coupled with a bit of teak on deck (handrails, forward hatch) and the modest stern overhang provide noticeable character. If you’re looking for an alternative to the similarly priced but more common 27-29 foot boats (Catalina 27, Hunter 27, O’day 28) of this age and price, check out an Irwin 28. She’s not a racer but she does offer good performance and accommodations for a small family looking for a friendly cruiser."