Another Ericson 27 owner here, a 1974 vintage. The 29 you reference is a sweet boat for that price. These boats are tough and well made with big bluewater trips still being made under those maintenance free, encapsulated keels.
In the smaller sizes, the Ericson is much like a top of the line Buick. Not a rocket in standard trim, but plenty of power for the highway, comfortable, spacious for the size, easy to operate and maintain, and a great value. The 29 would be an excellent first boat that will take you as far as the skipper can be prepared to go.
some of the less finer points I've discovered.
* The hull shape isn't optimal for DDW sailing. you will want to become proficient with poling out the genoa and sailing wing and wing, or live with a broad reach.
* Preventers are easy to rig and inexpensive. With the fin keel and spade rudder the boat can be twitchy and crash gybing is a real possibility. preventers are an inexpensive, highly functional upgrade.
* You may find the boat to be tender in moderate breeze, however, it will stiffen as the blow comes on. These boats are in their element in heavier air.
* 70's era masthead sloops have their drawbacks, and being designed for huge genoas is one of them. The main is embarrassingly small. Often one does not need to take a reef, but is more advised to be ready to change out the headsail for changing conditions. For breeze 20kts and up you need a working blade jib. Some people go for an 85% with a high clew, others have opted to run a 98~100% blade and fit a short run of tracks close to the cabin house to get a proper sheeting angle. Otherwise, just run a 135% with a reef or two and live with a close reach.
* likely the boat will be rigged with wire to rope halyards. new all rope halyards will require the mast to come down and new sheaves to be fit at the masthead. this is a great idea, anyway. at the same time you may want to upgrade the in-mast wires, windex, and potentially place your antenna up high. these boats are very simply rigged - new standing rigging should be part of your early plan, not considered optional.
* for heavy air I advise retrofitting the the split backstay with a backstay tensioner to tame the genoa and keep some tension on the forestay. These are relatively inexpensive and commonplace for any split backstay boat.
* the 27 and 29 both have a considerable amount of freeboard that can make for tricky docking in the breeze. out on the water I haven't found the tall sides to be an issue, but rather an asset: a dry cockpit. this is readily apparent to J/24 crew, soaked out of their minds and making fun of your Buick until they see that you're not in foulies and are comfortably sipping cappuccino with only one hand on the tiller.
* performance: a lot of people complain about these boats being slow, but the real issue seems to be mismatched expectations between a a 70's era, IOR influenced boat with masthead sails compared to newer ULDB boats and fractional rigs. Having said that, remember that Buick also made the Grand National.
On any old boat, new sails and more modern deck layout is the key upgrade.
good luck with whatever you decide. The 32 mkII would be a great step up from the 27 or 29 for both more space and performance. If you like the layout of the 29 and think you want more speed and a newer boat, I encourage you to consider the 28+ and the 30+ which are fractionally rigged and have deeper keels to boost performance. They are both sweet rides compared to the 70's era modesty of the 27 and 29.
I also encourage you to visit the fine folks at the Ericson owners site as previously suggested. They're a great bunch of folks with a great deal of experience with racing and cruising.